The　high　efficient　antireflective　down-conversion　Y2O3:Bi,Yb　films　with　nano-structure　pyramids　were　grown　successfully　on　Si　(100)　substrates　using　the　pulsed　laser　deposition　(PLD).　The　films　microstructure　can　be　controllably　tuned　only　by　changing　the　oxygen　pressure　in　PLD　process.　With　the　increasing　of　the　oxygen　pressure,　the　surface　morphology　changes　from　smooth　surface　to　pyramid　nano-structure,　and　the　preferential　orientation　of　films　changes　from　(222)　to　(400).　Besides,　the　average　reflectance　of　the　films　decreases　first　and　then　increases,　giving　a　minimum　value　of　15.8%　at　5　Pa　as　the　oxygen　pressure　increases,　which　is　comparable　to　that　of　uniform　pyramidal　micro-textured　surfaces　with　an　average　reflectance　of　13%-15%　fabricated　by　the　complicated　chemical　etching　method.　Moreover,　upon　excitation　of　ultraviolet　photon　varying　from　300　to　400　nm,　near　infrared　emission　of　Yb3+　due　to　transition　of　the　F-2(5/2)-＞　F-2(7/2)　was　observed　for　all　samples,　which　can　be　efficiently　absorbed　by　silicon　solar　cell.　These　pyramid　nano-structure　down-conversion　Y2O3:Bi,Yb　films　possess　promising　applications　in　enhancement　of　energy　efficiency　for　crystalline　Si　solar　cells　by　light　trapping　and　spectrum　shifting.　(C)　2012　American　Institute　of　Physics.　[http://dx.doi.org/10.1063/1.4712461]